It is often desirable for data processing equipment for example, personal computers, to be accessible for use only to authorized persons. Furthermore, individual components of such equipment should be protected against unauthorized removal. Given the proliferation of such equipment in the work place and the home and the resulting security requirements, it is no longer adequate after using the equipment to merely electrically switch the apparatus off with a key switch. In order to ensure the security of the equipment, the housing of the apparatus must also be simultaneously mechanically locked. With personal computers, there is the additional problem of separately protecting the drive assemblies for the external data carriers (floppy discs, etc.) so that data carriers potentially left behind in the drive assemblies after use cannot be removed. In order to achieve this, the equipment is provided with a covering that can be placed in front of the drive assemblies, this covering being advantageously lockable with the same key switch with which the apparatus can be electrically turned off and with which the housing can be mechanically locked.
German Utility Model Application G 88 07 737.3 discloses a lock mechanism that performs these functions and, in particular, is suitable for personal computers. This lock mechanism includes a simple pivoted lever lock similar to those used, for example, as cassette locks, and also includes a micro-switch and a lock bolt. Two pivoted levers are rigidly connected to the swiveling axis of the pivoted lever lock. The lock bolt is displaceable transversely relative to the swiveling axis and includes an engagement region for one of the pivoted levers. A tension spring is secured to the lock bolt, this tension spring pulling the bolt into a locking position. In the locking position, the lock bolt has a nose provided at its one end that engages an opening or recess in a covering. The covering can be positioned in front of the drive assemblies of the personal computer. The other end of the lock bolt includes an angled arm that, in the unlocking position of the lock bolt, actuates the micro-switches to turn the power supply on and off. When the swiveling axis of the pivoted lever lock swivels from the locking position into the unlocking position, one of the swivel arms of the pivoted lever lock contacts the engagement region of the lock bolt and pushes it back against the force of the tension spring. Simultaneously, the second swivel arm pivots out from behind a retaining element that is attached to the housing of the personal computer. When pivoted in the opposite direction, the swivel arm cooperating with the engagement region of the lock bolt slides out of the engagement region and releases lock bolt. Due to the force of the tension spring, the lock bolt is urged towards the locking position. Since the pivoted lever lock does not have its own spring assistance, the lock can potentially rest at an intermediate position between the respective final positions of the pivoted lever lock, even though the final positions are marked. For this reason, a tension spring is secured to one of the swivel arms to act as an over-dead-center spring, this tension spring pulling the pivoted lever lock into one or the other final position.
German Utility Model Application G 88 07 728.4 discloses another lock mechanism including a pivoted lever lock of the above described type having a leaf spring employed for spring assistance. This lock mechanism does not include a lock bolt.